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Topic: How many HC-SR04 sensors (Read 993 times)

My first attempt at a robot has 2 ultrasonic sensors slightly off to the left and right. They are run by a Picaxe 20X2 and the robot is managed by an IOIO / Android. They seem to work... sometimes. I always get a good signal when the robot is idle or being tested, but when it zooms across the room it tends to have a lot of crashes.

Can anyone guide me on a good number of sensors and where it's effective to place them please?

Soft and narrow objects can be a problem with the US sensors.It can still be a a loose wire or other problem so try setting up a controlled environment to pin point the issues.Even some cardboard set up as walls would be helpful to determine if the sensors and code is working or if there is a hardware problem.

Also, only run one sensor at a time! Wait some amount of time (say, 30-50 milliseconds) before running the other sensor, and do them ping-pong style, else you may get crosstalk.You can mount them so they sense in an "X" pattern -- turn the leftmost to face right, and rightmost to face left. This gives you some amount of "center" sensing, hopefully enough to avoid a crash.Also, try going slowly, not allowing a very fast top speed, until it's all tuned and working well. Then slowly increase max speed.

Finally, to compensate for the shortcomings of US sensors, you can also use a Sharp IR sensor, which works great for soft textiles, but is narrower in its sensing pattern. I use both on my rover robot.